Nanocarbon producing device and nanocarbon producing method

ABSTRACT

A surface of a graphite target ( 139 ), irradiated with a laser beam ( 103 ), is formed in a plane. The graphite target ( 139 ) is held by a target holding unit ( 153 ) on a target supply plate ( 135 ). A plate holding unit ( 137 ) moves the target supply plate ( 135 ) in a translational manner, which allows an irradiation position of the laser beam ( 103 ) and the surface of the graphite target ( 139 ) to be relatively moved. A transportation pipe ( 141 ) communicated with a nanocarbon collecting chamber ( 119 ) is provided toward a direction in which a plume ( 109 ) is generated, and a generated carbon nanohorn aggregates ( 117 ) is collected in the nanocarbon collecting chamber ( 119 ).

TECHNICAL FIELD

The present invention relates to a nanocarbon production apparatus and amethod of producing a nanocarbon.

BACKGROUND ART

Recently technological application of nanocarbon is actively studied.The nanocarbon means a carbon substance having a nanoscale finestructure, typified by a carbon nanotube, a carbon nanohorn, and thelike. Among these, the carbon nanohorn has a tubular structure in whichone end of the carbon nanotube formed by a cylindrically roundedgraphite sheet is formed in a circular conic shape, and the carbonnanohorn is expected to be applied to various technical fields due tospecific characteristics of the carbon nanohorn. Usually the carbonnanohorn is aggregated in a form, in which the circular conic portion isprojected to a surface like a horn while the tube is located in thecenter by Van der Waals force acting between circular conic portions.

It is reported that the carbon nanohorn aggregates is produced by alaser evaporation method of irradiating the carbon substance(hereinafter also referred to as “graphite target”) of a raw materialwith a laser beam in an inert gas atmosphere (Iijima, S., and other sixauthors, Chemical Physics Letter, ELSEVIER, 309 (1999) 165-170.). InIijima, S., and other six authors, Chemical Physics Letter, ELSEVIER,309 (1999) 165-170, it is described that a cylindrical graphite targetis rotated about an axis to irradiate a side face of the graphite targetwith the laser beam.

DISCLOSURE OF THE INVENTION

However, in the case where the laser beam irradiation is performed alongthe side face of the cylindrical graphite target, sometimes displacementof the laser beam irradiation position is generated. Further, thegraphite target surface irradiated with the laser beam once isroughened. When the roughened region is irradiated with the laser beamagain, a light irradiation area is easy to change in a side face of thegraphite target.

Therefore, a fluctuation in power density of the light with which theside face of the graphite target is irradiated is generated, whichsometimes decreases a yield of carbon nanohorn aggregates.

In view of the foregoing, an object of the invention is to provide atechnology which stably produces the carbon nanohorn aggregates in largevolume. Another object of the invention is to provide a technology whichstably produces the nanocarbon in large volume.

According to the invention, there is provided a nanocarbon productionapparatus comprising a target holding unit which holds a sheet-like orrod-shaped graphite target; a light source which irradiates a surface ofsaid graphite target with light; a moving unit which moves one of saidgraphite target and said light source relative to the other to move anirradiation position of said light in the surface of said graphitetarget, said graphite target being held by said target holding unit; andcollecting unit which collects carbon vapor to obtain nanocarbon, thecarbon vapor is vaporized from said graphite target by the irradiationof said light.

The nanocarbon production apparatus according to the invention comprisesa target holding unit which holds the sheet-like or rod-shaped graphitetarget. The nanocarbon production apparatus of the invention alsocomprises a moving unit which moves one of the graphite target and thelight source relative to the other. Therefore, the graphite targetsurface may be irradiated with the light while the relative positions ofthe graphite target and the light source are moved.

In the case where the conventional cylindrical graphite target surfaceis irradiated with the light while rotated, because a curved surface isirradiated with the light, the irradiation position displacement has alarge influence on a change in irradiation angle, which results in easygeneration of the fluctuation in power density. On the contrary, in theinvention, since the surface of the sheet-like or rod-shaped graphitetarget is irradiated with the light, even if the irradiation position isdisplaced, the light irradiation angle is difficult to change on thegraphite target surface. Therefore, the power density may easily becontrolled on the surface irradiated with the light, so that thefluctuation in power density may be suppressed. Therefore, quality ofnanocarbon may be stabilized, and the yield of nanocarbon may beimproved. Accordingly, the nanocarbon may stably be produced in largevolume.

As used herein, the term “power density” shall mean the power density ofthe light with which the graphite target surface is actually irradiated,namely, the power density at the light irradiation region in thegraphite target surface. Further, in the invention, the graphite targetsurface may be formed in a plane. Therefore, the change in power densitycaused by the light irradiation position displacement may be suppressedmore securely.

According to the invention, there is a method of producing a nanocarboncomprising a step of vaporizing carbon vapor from a sheet-like orrod-shaped graphite target by irradiating a surface of said graphitetarget with light while moving an irradiation position of the light; anda step of collecting said carbon vapor to obtain nanocarbon.

In a method of producing a nanocarbon according to the invention, thesurface of the sheet-like or rod-shaped graphite target is irradiatedwith the light, so that the fluctuation in power density caused by thelight irradiation position displacement may be suppressed. Therefore,the nanocarbon quality may be stabilized, and the yield of nanocarbonmay further be improved. Accordingly, the nanocarbon may stably beproduced in large volume.

In a nanocarbon production apparatus of the invention, said moving unitmay be configured to move the irradiation position of said light whilesubstantially keeping an irradiation angle constant at said irradiationposition in the surface of said graphite target.

In a method of producing a nanocarbon of the invention, a step ofirradiating the surface of said graphite target with said light suchthat an irradiation angle is substantially kept constant to the surfaceof said graphite target may be comprised.

Therefore, the graphite target surface may be irradiated with the lightat a constant irradiation angle, while the graphite target iscontinuously fedat the light irradiationposition. Accordingly, thefluctuation in power density of the light with which the graphite targetsurface is irradiated may be suppressed more securely, which allowsnanocarbon to be stably produced in large volume.

In a nanocarbon production apparatus of the invention, said moving unitmay be configured to move the irradiation position of said light whilecausing said graphite target to disappear at a point irradiated withsaid light.

In a method of producing a nanocarbon of the invention, the irradiationposition of said light may be moved in the surface of said graphitetarget while said graphite target is caused to disappear at a pointirradiated with said light.

In the invention, the light irradiation is performed while the graphitetarget is moved at the light irradiation position, and the graphitetarget is caused to disappear from the position irradiated with thelight. As used herein, the term “disappearance of graphite target”should mean that only an area having a predetermined depth is notvaporized and removed from the graphite target surface, but theirradiated area is completely removed in the depth direction and lightre-irradiation is not required.

According to this configuration, the graphite target may be efficientlyused while the supply and consumption of the graphite target are indexedto each other. Since the graphite target may be caused to disappearwithout re-irradiating the position irradiated with the light once inthe graphite target surface, the graphite target may be used up by theone-time light irradiation. In the position irradiated with the lightonce, the fluctuation in power density is easily generated inirradiating the position again because unevenness is generated in thesurface. However, this configuration may more securely suppress thefluctuation in power density of the light with which the graphite targetsurface is irradiated. Therefore, the nanocarbon quality may bestabilized, and the yield of nanocarbon may further be improved.

In a nanocarbon production apparatus of the invention, a control unitwhich controls action of said moving unit or said light source such thatpower density of said light, with which the surface of said graphitetarget is irradiated, is kept constant may further be comprised.Therefore, the power density of the light with which the graphite targetsurface is irradiated may be controlled more securely, which enables theconfiguration in which the nanocarbon having stable quality may beproduced with high yield.

In a nanocarbon production apparatus of the invention, said moving unitmay be configured to move said graphite target held by said targetholding unit in a translational manner. The provision of a rotatingmechanism which rotates the graphite target is not required by theconfiguration in which the graphite target is moved in the translationalmanner, which allows the apparatus configuration to be simplified. Afluctuation in power density of the light with which the graphite targetsurface is irradiated is easily suppressed by moving the rod-shaped orsheet-like graphite target in the translational manner. Therefore, thenanocarbon quality may further be stabilized. Further, the yield ofnanocarbon may be improved.

In a nanocarbon production apparatus of the invention, an endlessbelt-shaped graphite target may be installed to be entrained between apair of rollers such that said moving unit rotates said roller to drivesaid graphite target. Therefore, the graphite target may efficiently bedelivered to the light irradiation position. At this point, the powerdensity of the irradiation light becomes easy to control. The apparatusmay be miniaturized by the configuration in which the endlessbelt-shaped graphite target is installed between the pair of rollers. Inthe invention, the number of rollers included in “pair of rollers” maybe two or three or more.

In a nanocarbon production apparatus of the invention, said graphitetarget is a sheet-like graphite target wound about a rotating body, andsaid moving unit may be configured to push out said graphite target inthe direction of the irradiation position of said light while rotatessaid rotating body, said graphite target being released from saidrotating body. The apparatus can further be miniaturized by theconfiguration in which the graphite target is wound about the rotatingbody. The sheet-like graphite target may continuously be fed to thelight irradiation position by pushing out a portion which is releasedfrom the rotating body to spread the winding in the graphite target inthe direction of the light irradiation position. Further, since theamount of graphite target used in one-time production may be increased,the configuration more suitable for the volume production may berealized.

In a nanocarbon production apparatus of the invention, the nanocarbonmay be carbon nanohorn aggregates.

In a method of producing a nanocarbon of the invention, the step ofcollecting the nanocarbon may include a step of collecting carbonnanohorn aggregates.

Therefore, the carbon nanohorn aggregates may efficiently be produced inlarge volume. In the invention, the carbon nanohorn constituting thecarbon nanohorn aggregates may be formed in a single-layer carbonnanohorn or a multi-layer carbon nanohorn.

In the nanocarbon production apparatus, the carbon nanotube may also bethe nanocarbon.

In the method of producing the nanocarbon of the invention, the step ofirradiating the graphite target surface with the light may include astep of irradiating the graphite target surface with the laser beam.Therefore, because a wavelength and an orientation of the light may bekept constant, the light irradiation conditions for the graphite targetsurface may be controlled with high accuracy, which allows the desirednanocarbon to be selectively produced.

Thus, according to the invention, the nanocarbon may stably be producedin large volume. Further, according to the invention, the carbonnanohorn aggregates may stably be produced in large volume.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the inventionwill be apparent from the following description of preferred embodimentsand appended drawings in which:

FIG. 1 is a side view showing a configuration of a nanocarbon productionapparatus according to an embodiment;

FIG. 2 is a view showing a configuration of a nanocarbon productionapparatus according to an embodiment;

FIG. 3 is a side view showing a configuration of a nanocarbon productionapparatus according to an embodiment;

FIG. 4 is a side view showing a configuration of a nanocarbon productionapparatus according to an embodiment;

FIG. 5 is a side view showing a configuration of a nanocarbon productionapparatus according to an embodiment;

FIG. 6 is a view illustrating a shape of a graphite target which isapplicable to a nanocarbon production apparatus according to anembodiment;

FIG. 7 is a view illustrating a shape of a graphite target which isapplicable to a nanocarbon production apparatus according to anembodiment;

FIG. 8 is a view for explaining process management method in ananocarbon production apparatus according to an embodiment;

FIG. 9 is a view for explaining a method of producing a nanocarbonaccording to an embodiment; and

FIG. 10 is a view for explaining a laser beam irradiation angle.

BEST MODE FOR CARRYING OUT THE INVENTION

Taking the case where the nanocarbon is the carbon nanohorn aggregatesas an example, preferred embodiments of a nanocarbon productionapparatus and a method of producing a nanocarbon according to theinvention will be described below.

First Embodiment

FIG. 1 is a side view showing an example of a configuration of ananocarbon production apparatus. In the specification, FIG. 1 and otherdrawings used for the description are a schematic view, and thedimension of each component does not always correspond to an actualdimension ratio.

A nanocarbon production apparatus 125 of FIG. 1 includes two chambers ofa producing chamber 107 and a nanocarbon collecting chamber 119. Aninert gas supply unit 127 is connected to a producing chamber 107through a flowmeter 129. A laser beam 103 outgoing from a laser source111 held by a light source holding unit 112 is transmitted through aZnSe planoconvex lens 131 and a ZnSe window 133, and the surface of agraphite target 139 placed in the producing chamber 107 is irradiatedwith the laser beam 103.

The graphite target 139 is a target made of a solid-state carbon simplesubstance which is irradiated with the laser beam 103. The graphitetarget 139 is held by the target holding unit 153 on a target supplyplate 135. The plate holding unit 137 horizontally moves the targetsupply plate 135 in a translational manner. Therefore, when the targetsupply plate 135 is moved, the graphite target 139 placed thereon isalso moved, which allows an irradiation position of the laser beam 103and the surface of the graphite target 139 to be relatively moved.

FIG. 2(a) and FIG. 2(b) are a view for explaining the detailconfigurations of the target supply plate 135 and the plate holding unit137. FIG. 2(a) is a top view, and FIG. 2(b) is a sectional view taken online A-A′ of FIG. 2(a).

Screw heads are formed in a bottom surface of the target supply plate135 and the surface of the plate holding unit 137, and the target supplyplate 135 can be moved in a horizontal direction of FIG. 2(b) in a rackand pinion. Because a convex portion 157 of the target holding unit 153is slidably latched in a groove portion 155 of the target supply plate135, the graphite target 139 held by the target holding unit 153 and thetarget holding unit 153 is configured to be able to be moved in avertical direction of FIG. 2(a).

The above configuration enables the sheet-like graphite target 139 to bemoved in a p₁-q₁ direction and a p₁-q_(n) direction. Therefore, thegraphite target 139 can two-dimensionally be moved in a plane, whichallows the graphite target 139 to be fed at the irradiation position ofthe laser beam 103 outgoing from the laser source 111.

In the first embodiment, the irradiation position of the laser beam 103is moved in the graphite target 139 such that the power density of thelight on the surface of the graphite target 139 is irradiated becomessubstantially constant. For example, the irradiation angle orirradiation light intensity of the laser beam 103 is adjusted. Forexample, in the case where the surface of the graphite target 139 is theplane, the laser source 111 is placed such that the irradiation angle ofthe laser beam 103 becomes constant, and the graphite target 139 can bemoved in the translational manner while irradiated with the laser beam103 at constant intensity.

Returning to FIG. 1, a transportation pipe 141 is communicated with thenanocarbon collecting chamber 119. The transportation pipe 141 isprovided toward a direction in which a plume 109 is generated when thesurface of the graphite target 139 is irradiated with the laser beam 103from the laser source 111. In FIG. 1, because the surface of thegraphite target 139 is irradiated with the laser beam 103 which forms anangle of 45° with the surface of the graphite target 139, the plume 109is generated in the direction perpendicular to the surface of thegraphite target 139. The transportation pipe 141 has the configurationin which a lengthwise direction of the transportation pipe 141 isarranged in the direction perpendicular to the surface of the graphitetarget 139. Therefore, carbon nanohorn aggregates 117 generated bycooling the carbon vapor is induced from the transportation pipe 141 tothe nanocarbon collecting chamber 119, and the carbon nanohornaggregates 117 is securely collected in the nanocarbon collectingchamber 119.

The shape of the solid-state carbon simple substance used as thegraphite target 139 is not particularly limited. However, for example,the graphite target 139 is formed in sheet-like or rod-shaped. Thegraphite target 139 is formed in sheet-like or rod-shaped, and theirradiation angle and the intensity of the laser beam 103 with which thesurface of the graphite target 139 is irradiated are kept constant.Therefore, the fluctuation in power density can be suppressed in thesurface to stably produce the carbon nanohorn aggregates 117. In thecase where the rod-shaped graphite target 139 is caused to slide towardthe lengthwise direction of the graphite target 139 while keeping theirradiation angle of the laser beam 103 constant, the irradiation of thelaser beam 103 can also be performed at constant power density in thelengthwise direction of the graphite target 139.

At this point, it is preferable that the irradiation angle ranges from30° to 60°. In the first embodiment, the irradiation angle should meanthe angle formed between the laser beam 103 and the perpendicular to thesurface of the graphite target 139 at the irradiation position of thelaser beam 103. Fig. 10 is a view for explaining the irradiation angle.FIG. 10(a) is a sectional view of the graphite target 139 when thesurface of the graphite target 139 is the plane, and FIG. 10(b) is asectional view of the graphite target 139 when the surface of thegraphite target 139 is the curved surface.

When the irradiation angle is set at angles of 30° or more, reflectionof the irradiation laser beam 103, i.e., the generation of opticalfeedback can be prevented. Direct impact of the generated plume 109 onthe planoconvex lens 131 through the ZnSe window 133 is suppressed,which allows the ZnSe planoconvex lens 131 to be protected. Adhesion ofthe carbon nanohorn aggregates 117 to the ZnSe window 133 can also besuppressed.

When the irradiation angle is set at angles of 60° or less, thegeneration of amorphous carbon is suppressed, and a ratio of the carbonnanohorn aggregates 117 in the product, i.e., the yield of the carbonnanohorn aggregates 117 can be improved.

As shown in FIG. 1, it is particularly preferable that the irradiationangle is set at 45°. When the surface of the graphite target 139 isirradiated with the laser beam 103 at the angle of 45°, the ratio of thecarbon nanohorn aggregates 117 in the product can further be increasedto improve the yield.

Thus, in the nanocarbon production apparatus of FIG. 1, since theirradiation position of the laser beam 103 can continuously be changedin the surface of the graphite target 139, the carbon nanohornaggregates 117 can continuously be produced. Further, since the powerdensity of the laser beam 103 with which the surface of the graphitetarget 139 is irradiated can easily be kept constant, the carbonnanohorn aggregates can stably be produced with high yield.

Then, a method of producing the carbon nanohorn aggregates 117 with theproduction apparatus of FIG. 1 will specifically be described.

High-purity graphite, e.g., sheet-like or rod-shaped sintered carbon orcompression molded carbon can be used as the graphite target 139.

The laser beam such as a high-power CO₂ gas laser beam is used as thelaser beam 103.

The graphite target 139 is irradiated with the laser beam 103 in theinert gas atmosphere using rare gas such as Ar and He, e.g., at apressure range of 10³ Pa to 10⁵ Pa. It is preferable that the inert gasatmosphere is generated after the producing chamber 107 is previouslydecompressed by exhausting, e.g., at a pressure of 10⁻² Pa or less by avacuum pump 143 to which a pressure gage 145 is connected.

In order to keep the power density of the laser beam 103 constant in thesurface of the graphite target 139, e.g., in order to keep the powerdensity in the range of 20±10 kW/cm², it is preferable to adjust theoutput, a spot diameter, and the irradiation angle of the laser beam103.

For example, the output of the laser beam 103 is set in the range of 1kW or more and 50 kW or less, more specifically in the range of 3 kW to5 kW. A pulse width of the laser beam 103 is set at a time 0.02 sec ormore, preferably 0.5 sec or more, and more preferably 0.75 sec or more.Therefore, accumulation of energy of the laser beam 103 with which thesurface of a graphite rod 101 is irradiated can sufficiently be secured,which allows the carbon nanohorn aggregates 117 to be efficientlyproduced. The pulse width of the laser beam 103 is set at a time 1.5 secor less and preferably 1.25 sec or less. Therefore, energy density inthe surface of the graphite rod 101 is fluctuated by excessively heatingthe surface, and the decrease in yield of the carbon nanohorn aggregatescan be suppressed. It is more preferable that the pulse width of thelaser beam 103 ranges 0.75 sec or more and 1 sec or less. Therefore,both a formation rate and the yield of the carbon nanohorn aggregates117 can be improved.

In the irradiation of the laser beam 103, a down time can be set at atime 0.1 sec or more and preferably 0.25 sec or more. Therefore,overheat in the surface of the graphite rod 101 can be suppressed moresecurely.

As described in FIG. 1, preferably the irradiation angle of the laserbeam 103 ranges 30° or more and 60° or less, and more preferably theirradiation angle set at 45°. The laser beam 103 with which the surfaceof the graphite target 139 can be set at a spot diameter ranging 0.5 mmor more and 5 mm or less.

The graphite target 139 is moved in the translational manner while thesurface of the graphite target 139 is irradiated with the laser beam103. At this point, it is preferable that the graphite target 139 ismoved such that the spot of the laser beam 103 is moved at a speedranging 0.01 mm/sec or more and 100 mm/sec or less. Specifically themoving speed of the graphite target 139 is set at a speed ranging 2.5mm/sec or more and 50 mm/sec or less. When the moving speed of thegraphite target 139 is set at a speed 50 mm/sec or less, the surface ofthe graphite target 139 is securely irradiated with the laser beam 103.When the moving speed of the graphite target 139 is set at a speed 2.5mm/sec or more, the carbon nanohorn aggregates 117 can efficiently beproduced.

A soot-like substance produced with the nanocarbon production apparatus125 mainly contains the carbon nanohorn aggregates 117. For example, thesoot-like substance is collected as the substance containing carbonnanohorn aggregates 117 by 90 wt % or more. Thus, the carbon nanohornaggregates 117 can be obtained with high yield by using the nanocarbonproduction apparatus 125. The quality of the obtained carbon nanohornaggregates 117 can be stabilized.

In the nanocarbon production appartus 125, the position of the graphitetarget 139 can be moved in the plane direction, so that the graphitetarget 139 can be used up by irradiating the graphite target 139 withthe laser beam 103. Since it is not necessary to particularly provide achamber or the like for collecting junk of the graphite target 139, theconfiguration of apparatus can be simplified and the apparatus can beminiaturized.

The shape, the particle size, the length, and the front end shape of thecarbon nanohorn constituting the carbon nanohorn aggregates 117, theinterval between carbon molecules or carbon nanohorns, and the like canbe controlled in various ways by the irradiation conditions of the laserbeam 103 and the like.

Second Embodiment

A second embodiment relates to another configuration of the nanocarbonproduction apparatus. In the second embodiment, the same component asthe nanocarbon production apparatus 125 described in the firstembodiment is designated by the same numeral, and the description willnot be described as appropriate.

FIG. 3 is a side view showing the configuration of the nanocarbonproduction apparatus according to the second embodiment. A nanocarbonproduction apparatus 149 as shown in FIG. 3 has the configuration inwhich the graphite target 139 is delivered by a belt conveyer method.

In the nanocarbon production apparatus 149, a cyclic sheet of thegraphite target 139 is placed on the side faces of cylindrical rollers161 through a target holding plate 159. The irradiation position of thelaser beam 103 in the surface of the graphite target 139 is moved byrotating the rollers in a predetermined direction.

In the graphite target 139, it is preferable that a portion supported bythe target holding plate 159 is irradiated with the laser beam 103. Thereason is as follows: In order to keep the power density of theirradiation light constant, it is preferable that the surface of theirradiation region is flat. On the other hand, in a corner portionswhich are not supported by the target holding plate 159, a curvature ofthe surface of the graphite target 139 is larger than that of theportion supported by the target holding plate 159.

The second embodiment has the configuration in which the endlessbelt-shaped graphite target 139 is placed on the side faces of therollers 161 and installed between the pair of rollers 161. Therefore,the amount of graphite target 139 can be increased in one-time treatmentwhen compared with the first embodiment. The graphite target 139 isconfigured to be driven by rotating the roller 161. Therefore, thesmooth surface of the graphite target 139 can stably and continuously befed at the irradiation position of the laser beam 103 by the simpleconfiguration, which allows the configuration to be more suitable forthe volume production.

In the second embodiment, as with the configuration described in thefirst embodiment with reference to FIG. 2, the groove portion (not shownin FIG. 3) is formed in the target holding plate 159, and the convexportion (not shown in FIG. 3) of the target holding unit (not shown inFIG. 3) is latched in the groove portion, which allows the graphitetarget 139 to be also moved in the direction perpendicular to the sheetof FIG. 3.

Third Embodiment

A third embodiment relates to another configuration of the nanocarbonproduction apparatus. In the third embodiment, the same component as thenanocarbon production apparatus l25 or the nanocarboon productionapparatus 149 described in the first and second embodiments isdesignated by the same numeral, and the description will be described asappropriate.

FIG. 4 is a side view showing the configuration of the nanocarbonproduction apparatus according to the third embodiment. Although ananocarbon production apparatus 151 of FIG. 4 has the same basicconfiguration as the nanocarbon production apparatus 125 of FIG. 1, thenanocarbon production apparatus 151 differs from the nanocarbonproduction apparatus 125 in that the graphite target 139 is wound arounda rotatable target support rod 179. The sheet-like or rod-shapedgraphite target 139 is wound as a roll around the target support rod179. An end-portion region of the graphite target 139 released from thewinding of the target support rod 179 is placed on the target supplyplate 135 and induced toward the light irradiation direction. The thirdembodiment has the configuration in which the graphite target 139 iscontinuously fed to the light irradiation position to obtain the carbonnanohorn aggregates 117 by sequentially delivering the graphite target139 toward the irradiation direction of the laser beam 103.

One end of the graphite target 139 is placed on the target supply plate135. The target support rod 179 is rotated about the center axis, andthe target supply plate 135 is moved on the plate holding unit 137 inthe translational manner, which feeds the graphite target 139 to theirradiation position of the laser beam 103.

In the nanocarbon production apparatus of FIG. 4, as with theconfiguration described in the first embodiment with reference to FIG.2, the groove portion (not shown in FIG. 4) is formed in the targetsupply plate 135, and the convex portion (not shown in FIG. 4) of thetarget holding unit (not shown in FIG. 4) is latched in the grooveportion, which allows the graphite target 139 to be also moved in thedirection perpendicular to the sheet of FIG. 4.

FIG. 5 is a side view showing a nanocarbon production apparatus havingthe different configuration in which the rollers deliver the graphitetarget 139. A nanocarbon production apparatus 163 of FIG. 5 has twopairs of rollers 165 which hold the graphite target 139 from both sides.The graphite target 139 is delivered toward the irradiation direction ofthe laser beam 103 by rotating the target support rod 179 and therollers 165.

As shown in FIG. 4 or FIG. 5, when the roll-shaped graphite target 139is configured to be delivered, the larger amount of graphite target 139can be treated at one time. Therefore, the third embodiment is moreavailable for the volume production of the carbon nanohorn aggregates117.

It is preferable that the graphite target 139 is formed on a substratesuch as a Cu plate. Therefore, a crack or a breakage generated in thegraphite target 139 can be suppressed when the roll-shaped graphitetarget 139 is delivered. In this case, a take-up unit which taken up thesubstrate after the graphite target 139 is vaporized may be provided inthe producing chamber 107.

Fourth Embodiment

In the above-described first to third embodiments, a thickness of thegraphite target 139 may be adjusted such that the graphite target 139 inthe irradiation portion is used up when the portion is irradiated withlaser beam 103 at plural times, e.g., twice. Then, a method of producingthe carbon nanohorn aggregates 117 by applying the sheet-like graphitetarget 139 to the nanocarbon production apparatus 125 of FIG. 1 will bedescribed as an example.

For example, in the case where the power density of the laser beam 103with which the surface of the graphite target 139 is irradiated is setat about 20 kW/cm², the thickness of the graphite target 139 which isvaporized by the one-time irradiation of the laser beam 103 has a depthof about 3 mm from the surface. Therefore, in this case, the thicknessof the graphite target 139 is set at about 6 mm.

In FIG. 2(a), the irradiation position of the laser beam 103 is movedfrom p₁ toward q₁ on the graphite target 139, and the graphite target139 is reversely moved to p₁ when the graphite target 139 is irradiatedto q₁. Thus, when the graphite target 139 is reciprocated once, thegraphite target 139 between p₁ and q₁ is completely vaporized anddisappears. Then, the irradiation position of the laser beam 103 ismoved downward from p₁ to p₂ in FIG. 2(a), and similarly the graphitetarget 139 is reciprocated once between p₂ and q₂. The graphite target139 can be used up by repeating the reciprocating irradiation top_(n)-q_(n).

As the number of times in the irradiation of the surface of the graphitetarget 139 with the laser beam 103 is increased, the irradiated surfacebecomes rougher, and sometimes the fluctuation of the power density isincreased. However, when the thickness of the graphite target 139 isformed as described above, the fluctuation in power density can besuppressed. Therefore, the yield of the carbon nanohorn aggregates 117can be improved.

The adjustment of the thickness of the graphite target 139 is notlimited to the case in which the graphite target 139 disappears when thegraphite target 139 is irradiated with the laser beam 103 twice. Forexample, the graphite target l39 may be set at the thickness such thatthe graphite target 139 disappears by the three-time irradiation oflaser beam 103. In this case, the graphite target 139 may be moved inthe vertical direction of FIG. 2(a) in each one and half reciprocatingmovements.

In the fourth embodiment, the pulse width and down time of the laserbeam 103 and the moving speed of the graphite target 139 are adjusted,and the carbon nanohorn aggregates 117 may be produced on the conditionthat the irradiation of the laser beam 103 is not performed when thegraphite target 139 disappears. Therefore, the irradiation of thecomponents except for the graphite target 139 with the laser beam 103due to the disappearance of the laser beam 103 can be suppressed, whichallows the carbon nanohorn aggregates 117 to be more stably producedwith high yield.

In the region irradiated with the laser beam 103, for example as withthe nanocarbon production apparatus shown in FIG. 1 or FIG. 5, thefourth embodiment may have the configuration in which the target supplyplate 135 is not provided in a lower portion of the graphite target 139.For example in the configuration shown in FIG. 3 or FIG. 4 in theirradiation position of the laser beam 103, the target supply plate 135may also not be provided in a lower portion of the graphite target 139.Therefore, the target supply plate 135 and the like cannot directly beirradiated with the laser beam 103 just when the graphite target 139disappears.

A buffer graphite target may be arranged in the region which isirradiated with the laser beam 103 just when the graphite target 139disappears. Therefore, degradation of the producing chamber 107 causedby the direct irradiation of the wall surface and the like of theproducing chamber 107 with the laser beam 103 can be suppressed moresecurely.

The graphite target 139 may be formed on the sheet made of a materialwhich is not excited by the irradiation of the laser beam 103.Therefore, the decrease in yield of the carbon nanohorn aggregates 117caused by the direct irradiation of the target supply plate 135 and thelike with the laser beam 103 just when the graphite target 139disappears can be suppressed.

Fifth Embodiment

In the fourth embodiment, the thickness of the graphite target 139 maybe adjusted such that the graphite target 139 in the irradiation portionis used up when the portion is irradiated with laser beam 103 once.

Since it is not necessary that the position irradiated with the laserbeam 103 once is irradiated with the laser beam 103 again, the surfaceirradiated with the laser beam 103 is always kept smooth. Therefore, thefluctuation in power density of the laser beam 103 with which thesurface of the graphite target 139 is irradiated can further besuppressed, which allows the production stability of the carbon nanohornaggregates 117 to be further improved.

In the case where the graphite target 139 is formed in the sheet shape,for example, the shapes having the surfaces shown in FIGS. 6(i a) and6(b) are formed.

FIG. 6(a) shows a flat plate, and the flat plate is preferable becausethe power density of the laser beam 103 is easily kept constant.

In FIG. 6(b), a regularly repeated structure is formed at predeterminedpitches on the surface of the graphite target 139. In this case, forexample when the laser beam 103 is moved in the p₁-q₁ direction, thefluctuation in power density can also be suppressed in the irradiationposition.

In the case where the graphite target 139 is formed in the shape shownin FIG. 6(b), it is preferable that a width w of the repeated structureis substantially equal to the spot diameter of the laser beam 103.Therefore, the power density of the laser beam 103 with which thesurface of the graphite target 139 is irradiated can be kept constant,when the graphite target 139 is irradiated with the laser beam 103 bymoving the light irradiation region in the graphite target 139 in thep₁-q₁ direction, after that in the p₂-q₂ direction, . . . , and theirradiation position of the laser beam 103 is sequentially moved in thep₁-p₅ direction. Therefore, fluctuation of the power density of thelaser beam 103 with which the surface of the one sheet of graphitetarget 139 is irradiated can be suppressed, and the carbon nanohornaggregates 117 having the desired characteristics can stably be obtainedwith high yield.

The shape of the graphite target surface may have the repeated structurewith the predetermined width w (pitch). The shape of the graphite targetsurface is not limited to the configuration shown in FIG. 6(b), and theshape can appropriately be selected.

In FIG. 6(a) and FIG. 6(b), a thickness h of the graphite target 139 isset to an extent in which the graphite target 139 is completelyvaporized by the one-time irradiation of the laser beam 103 as describedabove. For example, when the power density of the laser beam 103 withwhich the surface of the graphite target 139 is irradiated is about 20kW/cm², the thickness of the graphite target 139 vaporized by theone-time irradiation of the laser beam 103 has the depth of 3 mm fromthe surface, so that the thickness h can be set at about 3 mm.

In the fifth embodiment and the fourth embodiment, the graphite target139 may be formed in the rod shape such that the width of the graphitetarget 139 is substantially equal to the spot diameter of the laser beam103. Therefore, the moving direction of the graphite target 139 can beset only in the A-A′ direction of FIG. 2(a). Accordingly, it is notnecessary to form the movable mechanism by combining the groove portion155 and the convex portion 157 between the target supply plate 135 andthe target holding unit 153, the apparatus configuration can further besimplified.

FIG. 7 is a view showing an example of the shape of the rod-shapedgraphite target 139. FIG. 7(a) shows a quadratic prism graphite target139, and FIG. 7(b) shows a cylindrical graphite target 139. The shapesof the graphite target 139 are not limited to the shapes shown in FIGS.7(a) and 7(b). It is preferable that the graphite target 139 has a fixedcross-sectional shape. The fixed cross-sectional shape enables thesuppression of the fluctuation in power density of the laser beam 103with which the surface of the graphite target 139 is irradiated.

It is preferable that the maximum width w of the graphite target 139 isless than or equal to the spot diameter of the laser beam 103.Therefore, the laser beam 103 may be moved only in the lengthwisedirection of the graphite target 139, and the production process can besimplified. It is preferable that the thickness h of the graphite target139 is less than or equal to the spot diameter of the laser beam 103.Therefore, the graphite target at the irradiation position can securelybe caused to disappear by the one-time irradiation of the laser beam103.

Both the width w and the thickness h are less than or equal to the spotdiameter of the laser beam 103, and the surface of the graphite target139 is irradiated with the laser beam 103 along the lengthwise directionof the rod-shaped laser beam 103. Therefore, the graphite target 139 canbe used up by the one-time irradiation.

Further, similarly to the fourth embodiment, the fifth embodiment can beapplied to the nanocarbon production apparatus shown in FIG. 3 and FIG.4.

Sixth Embodiment

For example, process management in the above embodiments can beperformed as follows. FIG. 8 is a view for explaining the processmanagement method in the above nanocarbon production apparatus.

Referring to FIG. 8, a process management unit 167 performs schedulemanagement of each process based on time information inputted from atiming unit 169. The case in which the nanocarbon production apparatus125 (Fig. 1 and FIG. 2) of the first embodiment is used in the fourthembodiment will be described as an example of the schedule managementwith reference to a flowchart of FIG. 9.

First, a pump control unit 171 drives the vacuum pump 143 to decompressby exhausting the nanocarbon collecting chamber 119 and the producingchamber 107 communicated therewith (S101). When the decompression byexhausting is performed for a predetermined time, the vacuum pump 143 isstopped, and an inert gas control unit 173 supplies the constant amountof inert gas from the inert gas supply unit 127 into the producingchamber 107 (S102). Then, a laser beam control unit 175 performs theirradiation of the laser beam 103 (not shown in FIG. 8) having thepredetermined intensity from the laser source 111 (S103).

A moving means control unit 177 rotates the plate holding unit 137tomove the target supply plate 135 at a predetermined speed (S104). Thestep S104 corresponds to the movement of the graphite target 139 in thep-q direction in FIG. 2(a), and the graphite target 139 is moved suchthat, for example, the irradiation position of the laser beam 103 isreciprocated once between p₁ and q₁ in the surface of the graphitetarget 139.

When a predetermined time elapses (Yes in S105), and when the graphitetarget is not used up (No in S106), the moving means control unit 177moves the position of the target holding unit 153 latched in the targetsupply plate 135 (S107), and the steps from the step S104 are repeated.The step S107 corresponds to the movement of the graphite target 139 inthe p₁-p_(n) direction in FIG. 2(a), and the irradiation position of thelaser beam 103 is moved, e.g., from p₁ to p_(n).

The graphite target 139 is completely used to end the production of thecarbon nanohorn aggregates 117 by repeating the above operation untilthe graphite target 139 is used up (Yes in S106).

The above steps are managed by the process management unit 167.

In the process management shown in FIG. 8, the moving means control unit177 may relatively move one of the graphite target 139 and the lasersource 111 with respect to the other to move the irradiation position ofthe laser beam 103 in the surface of the graphite target 139. Forexample, the sixth embodiment may have the configuration in which themoving means control unit 177 adjusts the irradiation angle of the lasersource 111 irradiating the surface of the graphite target 139 with thelaser beam 103. Further, the sixth embodiment may have the configurationin which the irradiation of the laser beam 103 is performed while thelaser beam control unit 175 changes the outgoing light intensity of thelaser beam 103. Therefore, the power density of the laser beam 103 withwhich the graphite target 139 is irradiated can be adjusted moreprecisely.

Thus, the embodiments of the invention are described with reference tothe drawings. However, the above embodiments are illustrated by way ofexample only, and various configurations could be adopted besides theabove embodiments.

For example, in the above embodiments, the case in which the carbonnanohorn aggregates is produced is described as an example of thenanocarbon. However, the nanocarbon produced with the nanocarbonproduction apparatus according to the embodiments is not limited to thecarbon nanohorn aggregates.

For example, the carbon nanotube can also be produced with thenanocarbon production apparatus according to the embodiments. In thecase where the carbon nanotube is produced, it is preferable that theoutput, the spot diameter, and the irradiation angle of the laser beam103 are adjusted such that the power density of the laser beam 103 iskept constant, e.g. the power density is in the range of 50±10 kW/cm² inthe surface of the graphite target 139.

Metal catalyst, e.g., ranging 0.0001 wt % or more and 5 wt % or less isadded into the graphite target 139. Metal such as Ni and Co can be usedas the metal catalyst.

The graphite target 139 can continuously be delivered to the irradiationposition of the laser beam 103 by using the nanocarbon productionapparatus according to the embodiments. Therefore, in the production ofthe carbon nanotube, the carbon nanotube can stably be produced in largevolume.

The pieces of apparatus shown in FIG. 1, FIG. 3, FIG. 4, and FIG. 5 havethe configuration in which the soot-like substance obtained by theirradiation of the laser beam 103 is collected in the nanocarboncollecting chamber 119. In addition, the soot-like substance can becollected by depositing the soot-like substance on a proper substrate,or the soot-like substance can be collected by the method of collectingfine particles with a dust bag. Further, the inert gas can also becirculated in the reaction chamber to collect the soot-like substance bya flow of the inert gas.

In the pieces of apparatus shown in FIG. 1, FIG. 3, FIG. 4, and FIG. 5,the irradiation position of the laser beam 103 is fixed and the graphitetarget 139 is moved, which relatively moves the positions of the laserbeam 103 and the graphite target 139. However, the relative positionsmay be changed by holding the laser source 111 with the moving unit tomove the laser beam 103.

1. A nanocarbon production apparatus comprising: a target holding unitwhich holds a sheet-like or rod-shaped graphite target; a light sourcewhich irradiates a surface of said graphite target with light; a movingunit which moves one of said graphite target held by said target holdingunit and said light source relative to the other to move an irradiationposition of said light in the surface of said graphite target; and acollecting unit for collecting carbon vapor evaporated from the graphitetarget by irradiation with light, as nanocarbon
 2. A nanocarbonproduction apparatus according to claim 1, wherein said moving unit isconfigured to move the irradiation position of said light whilesubstantially keeping an irradiation angle constant at said irradiationposition in the surface of said graphite target.
 3. A nanocarbonproduction apparatus according to claim 1, wherein said moving unit isconfigured to move the irradiation position of said light while causingsaid graphite target located at a point irradiated with said light todisappear, said graphite target.
 4. A nanocarbon production apparatusaccording to claim 1, further comprising a control unit which controlsaction of said moving unit or said light source such that power densityof said light irradiated to the surface of said graphite target is keptconstant.
 5. A nanocarbon production apparatus according to claim 1,wherein said moving unit moves said graphite target held by said targetholding unit in a translational manner.
 6. A nanocarbon productionapparatus according to claim 1, wherein said graphite target isconfigured to drive it by installing an endless belt-shaped graphitetarget is between a pair of rollers, and rotating said roller with saidmoving unit.
 7. A nanocarbon production apparatus according to claim 1,wherein said graphite target is a sheet-like graphite target wound abouta rotating body, and said moving unit is configured to push out saidgraphite target released from said rotating body toward the direction ofirradiation position of said light while rotates said rotating body. 8.A nanocarbon production apparatus according to claim 1, wherein saidnanocarbon is carbon nanohorn aggregates.
 9. A method of producing ananocarbon comprising: vaporizing carbon vapor from a sheet-like orrod-shaped graphite target by irradiating a surface of said graphitetarget with light while moving an irradiation position of the light; andcollecting said carbon vapor to obtain nanocarbon.
 10. A method ofproducing a nanocarbon according to claim 9, further comprising:irradiating the surface of said graphite target with said light suchthat an irradiation angle is substantially kept constant to the surfaceof said graphite target.
 11. A method of producing a nanocarbonaccording to claim 9, the irradiation position of said light is moved inthe surface of said graphite target while said graphite target is causedto disappear at a point irradiated with said light.
 12. A method ofproducing a nanocarbon according to claim 9, wherein said nanocarbon iscarbon nanohorn aggregates.